1. Field of the Invention
The present invention relates to a semiconductor laser CRT for driving at room temperature, whose target is pumped by an electron beam.
2. Description of the Related Art
FIG. 1 is a cross-sectional view illustrating the schematic, configuration of a conventional semiconductor laser CRT. As shown in FIG. 1, the laser CRT essentially includes a vacuum glass bulb 3 having a laser target 2 housed at one end of the CRT and an electron gun 4 placed close to the other end thereof. The alignment of the electron beam focusing and deflecting means, i.e., magnets, surrounds the vacuum glass bulb 3 near the electron gun so that an electron beam is focused and projected through the laser target 2. The laser target 2 which is maintained at a high positive potential by a high voltage source (not shown) is housed on the inner surface of a transparent support plate 5 sealed in the end of the glass bulb 3. The laser target 2 is formed with a semiconductor structure, and includes a means for forming an existing Fabry-Perot resonator for sustaining stimulated emission of luminescence. That is, the resonator is formed of a pair of mirrors (not shown), which will be described later.
In the operation of the laser CRT, the high positive potential applied to the laser target 2 causes an electron beam to be attracted to and absorbed by the semiconductor structure of the laser target 2. The electron beam in this semiconductor structure generates electron-hole pairs. When electrons and holes are recombined with each other, they generate radiation. The light amplification by stimulated emission of the radiation depends on the pure gain of the resonator, and essentially generates an optical beam emitted perpendicularly to the surface of the laser target 2. Since the electron beam is incident upon the inner surface of the target at an angle of nearly 90xc2x0 to the target, the optical beam and the electron beam might be fundamentally considered straight. Thus, the optical beam can be made to scan by scanning the electron beam on the target.
In particular, in the laser CRT of FIG. 1, the transparent support plate 5, onto which the laser target 2 is mounted, is coupled to the glass bulb 3 by a metal ring 8. The metal ring 8 is formed with a structure in which a first covar-ring 8a and a second covar-ring 8b are combined with each other. Here, the first covar-ring 8a has a thermal expansion coefficient similar to that of the glass bulb 3, and is coupled to the glass bulb 3. The second covar-ring 8b has a thermal expansion coefficient that is similar to that of the transparent support plate 5 formed of sapphire or the like, and is coupled to the transparent support plate 5. A low temperature maintaining device 1, i.e., a cryostat, for cooling the laser target 2 is provided together with an auxiliary transparent support plate 6. Also, a vacuum-sealed glass tube 7 is provided to prevent heat transfer between the low temperature maintaining device 1 and the open air. Here, the cover-rings 8a and 8b are coupled respectively to the glass bulb 3 and the transparent support plate 5 by soldering or other methods. FIG. 2 is an exploded perspective view illustrating the covar-rings 8a and 8b disassembled respectively from the glass bulb 3 and the transparent support plate 5.
As shown in FIG. 1, the conventional laser CRT includes the low temperature maintaining device 1, but the low temperature maintaining device 1 is no longer necessary when the existing laser CRT is driven at room temperature. Besides, when the laser target 2 made of a III-V group compound such as GaN is used, a single crystal is directly grown on the transparent support plate 5 by metal organic chemical vapor deposition (MOCVD). Therefore, transparent sapphire plates must be used as the growth support plates 5 and 6 to each of the side surfaces of which the covar-ring 8 is attached. In this case, since the growing temperature in the MOCVD must be 800xc2x0 C. or more, a metal organic gas and a hydride gas entering a reactor react with the covar-rings. As a consequence, the covar-rings are easily eroded or other compounds are formed on the surfaces thereof, making a covar-to-covar bonding impossible. In contrast with the above, when the covar-rings are attached after the III-V group compound has been grown on the sapphire support plate, the single crystal structure and composition of the grown III-V group compound are destroyed by heat of 1000xc2x0 C. or more generated upon welding.
Such a covar-ring attaching method is complicated, the covar-ring required for the method is expensive, and airtight maintenance with respect to an internal vacuum is difficult. In particular as for the airtight maintenance, as shown in FIG. 2, even when there is a slight difference between the glass bulb 3 and the covar-ring 8a, the covar-ring 8a is expanded or shrunk excessively lager or smaller than the glass bulb 3 in directions indicated by the arrows, so that the glass bulb 3 is broken or the covar-ring 8a is separated from the glass bulb 3. As shown in FIG. 3, even though the covar-ring 18a is attached to the outer surface of the glass bulb 13 to prevent destroying the glass bulb due to the excessive expansion of the covar-ring, generation of a gap is inevitable.
Also, when the metallic covar-ring is used, the internal voltage of the glass bulb becomes low.
To solve the above problems, it is an objective of the present invention to provide a semiconductor laser CRT for driving at room temperature by which airtightedness of a glass bulb is achieved by using an adhesive material which substitutes for a metallic covar-ring and has the same thermal expansion coefficient as that of the metallic covar-ring.
Accordingly, to achieve the above objective, there is provided a semiconductor laser cathode ray tube (CRT) for driving at room temperature comprising: a laser target including a semiconductor substrate formed of a semiconductor compound, a front mirror layer formed on the semiconductor substrate, an active layer formed on the front mirror layer, and a rear mirror layer formed on the active layer; a transparent support substrate having the laser target mounted thereon; a glass bulb having an electron gun, for emitting an electron beam, installed therein; and an adhesive material for adhering the edge of the glass bulb to the edge of the transparent support plate.
Preferably, the transparent support plate is made of glass, and the adhesive material is made of frit glass.